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Background Heavy metal contamination in water and agricultural products is a major concern that causes risks for human health. This article describes a highly selective approach to preconcentrate cobalt(II) (Co(II)) ions based on the standard UV-visible measurement of Co(II)-1-(2-pyridylazo)-2-naphthol complex at λ = 628 nm in water and nut samples. In this method, magnetic silica (mSiO2 ) was utilized as a practical sorbent and 1-(2-pyridylazo)-2-naphthol was employed as a complexing agent in the elution step. The adsorbent was characterized via X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy. The effects of the main variables (pH, adsorption time, sorbent amount, pH of eluent, ligand volume, and desorption time) were investigated and established. Results The maximum recovery was achieved at pH 7 ± 0.3, adsorption time of 60 min, sorbent amount of 40 mg, eluent pH 8 ± 0.2, ligand volume of 2 mL (16.95 × 10-4 mol L-1 ) and desorption time of 30 min. The linearity of dynamic range (10-500 μg L-1 ), limit of detection (0.32 μg L-1 ), relative standard deviation (3.04%), and preconcentration factor (25) show the reliability of the method. The sorbent was reusable 12 times. Selectivity and the effect of interference ions were successfully examined. The adsorption process of Co(II) ions on mSiO2 was investigated based on Langmuir and Freundlich isotherms. The Freundlich model was fitted with the system and the maximum capacity adsorption of mSiO2 for Co(II) adsorption is 2.35 mg g-1 . Then, the kinetics study revealed that the adsorption process of Co(II) ions on the mSiO2 follows the pseudo-first-order model. The thermodynamics parameters ΔG, ΔS, and ΔH were calculated. Conclusion The method was fruitfully applied to preconcentrate Co(II) ions in water and nut samples. This method offers high selectivity and precision for determining Co(II) ions. © 2020 Society of Chemical Industry.

A facile headspace single drop microextraction method was developed using deep eutectic solvent-based magnetic bucky gel as the extraction solvent for the first time. The hydrophobic magnetic bucky gel was formed by combining choline chloride/chlorophenol deep eutectic solvent and magnetic multiwalled carbon nanotube nanocomposite. Magnetic susceptibility, high viscosity, high sorbing ability, and tunable extractability of organic analytes are the desirable advantages of the prepared gel. Using a rod magnet as a suspensor in combination with the magnetic susceptibility of the prepared gel resulted in a highly stable droplet. This stable droplet eliminated the possibility of drop dislodgement. The prepared droplet made it possible to complete the extraction process in high temperatures and elevated agitation rates. Furthermore, using larger micro-droplet volumes without any operational problems became possible. These facts resulted in shorter sample preparation time, higher sensitivity of the method, and lower detection limits. Under the optimized conditions, an enrichment factor of 520-587, limit of detection of 0.05-0.90 ng/mL, and linearity range of 0.2-2000 ng/mL (coefficient of determination = 0.9982-0.9995) were obtained. Relative standard deviations were

A new series of 1,4-diarylazetidin-2-one derivatives (β-lactams) were designed and synthesized to evaluate their biological activities as selective cyclooxygenase-2 (COX-2) inhibitors. In vitro COX-1 and COX-2 inhibition studies showed that all compounds were selective inhibitors of the COX-2 isozyme with IC50 values in the 0.05-0.11 µM range, and COX-2 selectivity indexes in the range of 170-703.7. Among the synthesized β-lactams, 3-methoxy-4-(4-(methylsulfonyl)phenyl)-1-(3,4,5-trimethoxyphenyl)azetidin-2-one (4j) possessing trimethoxy groups at the N-1 phenyl ring exhibited the highest COX-2 inhibitory selectivity and potency, even more potent than the reference drug celecoxib. The analgesic activity of the synthesized compounds was also determined using the formalin test. Compound 4f displayed the best analgesic activity among the synthesized molecules. Molecular modeling studies indicated that the methylsulfonyl pharmacophore group can be inserted into the secondary pocket of the COX-2 active site for interactions with Arg513 . The structure-activity data acquired indicate that the β-lactam ring moiety constitutes a suitable scaffold to design new 1,4-diarylazetidin-2-ones with selective COX-2 inhibitory activity.

The collision-induced dissociation of the protonated five-arm star propoxylated diethylenetriamine polyols was studied under electrospray conditions. Two product ion series were detected because of the cleavage of the C-N bonds in the initiator moiety. No backbone fragmentation of the polyether chains was observed, which allowed to explore the initiation and side-chain propagation process of the oligomers. On the basis of MS/MS spectra, it is probable that the rate of the initiation is larger than that of the chain propagation. The propylene oxide repeat units attach to the five arms with approximately the same probability. Furthermore, it was found that the collision energy necessary to obtain 50% fragmentation (CE50) was linearly dependent on the molecular weight of the polyols.

Application of treated sawdust with NaOH as a green and economical sorbent for simultaneous preconcentration of trace amounts of Cd(II), Co(II), and Pb(II) ions from liver, lettuce, fish, and water as test samples with complicated matrices was investigated. Various parameters, such as effect of pH and contact time, breakthrough volume, type, and concentration of eluent and interference of ions were studied. The sorption was quantitative in the pH of 5.0 to 7.0 and desorption occurred instantaneously with 5.0 mL of mixed solutions of ethanol and 2.0 mol/L HNO3–HCl and the amount of ions was measured by using flame atomic absorption spectrometry. Linearity was maintained at 3 to 500 μg/L for cobalt, 5.0 to 800 μg/L for lead, and 2.0 to 300 μg/L for cadmium in the original solution. The relative standard deviation was less than 1.80% (n = 6, with concentration of 0.3 mg/L for cadmium and 0.5 mg/L for lead and cobalt). Detection limits and maximum capacity of the sorbent for Co (II), Cd (II), and Pb (II) in the original solution were 0.86, 0.50, and 1.7 μg/L and 28.5, 30.6, and 47.3 mg/g, respectively. The results for spiked real samples, effect of interfering ions, and adsorption capacity indicated that the applicability of this method for lead preconcentration is better than cadmium and cobalt preconcentration from complicated matrices. Practical Application: Sawdust can be applied as a green and economical sorbent for simultaneous preconcentration and solid-phase extraction of metal ions from food and environmental samples with complicated matrices.

Dissociation of doubly cationized polyethers, namely [P + 2X]2+ into [P + X]+ and X+, where P = polyethylene glycol (PEG), polypropylene glycol (PPG) and polytetrahydrofuran (PTHF) and X = Na, K and Cs, was studied by means of energy-dependent collision-induced dissociation tandem mass spectrometry. It was observed that the collision voltage necessary to obtain 50% fragmentation (CV50) determined for the doubly cationized polyethers of higher degree of polymerization varied linearly with the number of degrees of freedom (DOF) values. This observation allowed us to correlate these slopes with the corresponding relative gas-phase dissociation energies for binding of alkali ions to polyethers. The relative dissociation energies determined from the corresponding slopes were found to decrease in the order Na+ > K+ > Cs+ for each polyether studied, and an order PPG ≈ PEG > PTHF can be established for each alkali metal ion. Copyright © 2011 John Wiley & Sons, Ltd.

A novel, simple, fast, and efficient ionic liquid-based dispersive liquid–liquid extraction (IL-DLLE) has been applied to extract and remove Congo Red (CR; a carcinogenic textile dye) from aqueous solutions. In this methodology a binary solution, containing the extraction solvent (1-hexyl-3-methylimmidazolium bis(trifluormethylsulfonyl) imid) and a suitable disperser solvent, was rapidly injected into the water sample containing CR dye. Therewith, a cloudy solution was formed, and most of the dye molecules were extracted into fine IL droplets and removed from aqueous phase. The effects of pH, type, and amount of IL, initial concentration of the dye, type and volume of the dispersant, and concentrations of salt on the extraction of the dye were studied. Experimental surveys were also accomplished for recovery of the IL by applying a reverse dispersive liquid–liquid extraction using acidic stripping solutions.

The present study reports a novel sample enrichment method termed supramolecular-based dispersive liquid-liquid microextraction (SM-DLLME). The SM solvent selected was made up of reversed micelles of decanoic acid dispersed in tetrahydrofuran (THF)-water. THF plays double role, not only acts as a disperser solvent but also causes self-assembly of decanoic acid. The contaminant used as a model was Malachite Green (MG). It was a cationic dye and was preconcentrated without any derivatization or ion-pair formation reaction. In SM-DLLME, the most important advantages of DLLME technique and preconcentration strategy based on the coacervation and reverse micelles have come together. Moreover, in this method, disadvantages of DLLME such as extraction capability of only hydrophobic analytes and hiring toxic and hazardous organic solvents as the extraction solvent and disadvantages of coacervation-based extraction method such as tedious, labor-intensive and time-consuming stirring procedure have been avoided. Several variables affecting the microextraction efficiency were investigated and optimized. Under the optimized conditions and preconcentration of only 5.00 mL of sample, the enhancement factor was 52, limit of detection (LOD) was 4 μg/L and relative standard deviations (RSDs) for 145 and 36 μg/L of MG in textile industry wastewater were 1.8 and 3.2%, respectively (n = 6).

A simple and reliable method for rapid and selective extraction and determination of trace levels of Ni2+ and Mn2+ was developed by ionic liquid (IL) based dispersive liquid–liquid microextraction coupled to flame atomic absorption spectrometry (FAAS) detection. The proposed method was successfully applied to the preconcentration and determination of nickel and manganese in soil, vegetable, and water samples. After preconcentration, the settled IL-phase was dissolved in 100 µL of ethanol and aspirated into the FAAS using a home-made microsample introduction system. Injection of 50 µL of each analyte into an air–acetylene flame provided very sensitive spike-like and reproducible signals. Effective parameters such as pH, amount of IL, volume of the disperser solvent, concentration of the chelating agent, and effect of salt concentration were inspected by a (25-1) fractional factorial design to identify the most important parameters and their interactions. Under optimum conditions, preconcentration of 10 mL sample solution permitted the detection of 0.93 µg L−1 Ni2+ and 0.52 µg L−1 Mn2+ with enrichment factors 77.2 and 82.6 for Ni2+ and Mn2+, respectively. The accuracy of the procedure was evaluated by analysis of a certified reference material (CRM TMDW-500, drinking water).

To assess and compare the current management of sudden sensorineural hearing loss (SSHL) between primary care physicians and general otolaryngologists.Written survey of physician practice patterns.A multiple choice and Likert scale survey was mailed to 1306 otolaryngologists and primary care physicians in the upper midwest with respect to management of SSHL.A significant number of general practitioners treat SSHL independent of an otolaryngologist. General practitioners are significantly less impressed than otolaryngologists that steroids are an effective treatment (P0.0001). Over 98 percent of otolaryngologists use oral steroids as compared with 73 percent of general practitioners treating on their own. The vast majority of otolaryngologists start therapy with at least 60 mg of prednisone whereas lower doses and medrol dosepaks are more commonly used by general practitioners. Otolaryngologists are more likely to treat with steroids beyond one week of onset of hearing loss whereas general practitioners overwhelmingly will only treat within the first week. Approximately 50 percent of otolaryngologists add antiviral medications in contrast to 16 percent of generalists.The approach to SSHL differs between otolaryngologists and general practitioners. The lack of strong evidence-based guidelines for the treatment of SSHL may underlie the variability in management by first line providers.

A streamline upwind formulation is presented for the treatment of the advection terms in the general transport equation. The formulation is monotone and conservative and is based on the discontinuous nature of the advection mechanism. The results of there benchmark test cases for the full range of flow Peclet numbers are presented. The new formulation is shown to accurately model the advection phenomenon with significantly smaller numerical diffusion than the existing methods. The results are also free of all spatial oscillations. Considerable savings in computer storage and execution time have been achieved by employing the three-noded triangular element for which exact integrations exist. The formulation is straightforward and can be readily incorporated into any finite element code using the conventional Galerkin approach.